U.S. Pat. No. 4,190,397 assigned to the assignee of the present invention describes in detail the need for and use of windage shields in gas turbine engines. In particular, it is pointed out in that patent that efficiency of the engine can be shown to be directly related to the ability of the engine to operate at higher turbine inlet temperatures. This need for higher turbine operating temperatures has required cooling air to be supplied to various components of the engine in order to allow the components to operate at the higher temperatures without damaging thermal stress. In order to supply cooling air to these components at a temperature which is effective to lower the temperature of the operating components, cooling air is extracted from a compressor section of the engine and routed through various channels to the turbine section. As the cooling air is subjected to work input in passing through these channels, the temperature of the cooling air rises. Elements which have been found to significantly affect work in the cooling fluid flow are nuts and bolt heads utilized in connecting various sections of the turbine together. These nuts and bolt heads protrude into the cooling air channels creating "drag" and cause the cooling fluid to change velocity in such a manner that cooling air receives more work. The aforementioned U.S. Patent describes a windage shield which improves the performance of gas turbine engines over prior windage shields. The windage shield described therein is particularly useful with bolted flange connections which protrude into the fluid flow passage and are connected together by bolts with heads in the fluid flow passage. The described windage shield comprises a continuous ring of generally L-shaped profile which is captured between the bolt head and the upstream most flange. The captured flange portion of the shield is provided with a plurality of circumferentially spaced milled slots contoured to receive D-shaped bolt heads. These bolt heads are mounted flush with the upstream captured portion of the shield, thus eliminating open access holes and protruding bolts. The combination of D-shaped heads and contoured slots provides a means for torquing the bolts. The cylindrical section of the L-shaped shield extends downstream of the mating flanges and pass the nut side of the bolted connection to direct cooling air past the nut, thereby minimizing velocity reduction from the nut.
While the invention as described in the aforementioned U.S. Pat. No. 4,190,397 is effective to reduce windage effects within the fluid flow channel of a gas turbine engine, the windage shield described in that patent does require that a plurality of contoured slots be machined in the surface of the windage shield facing the fluid flow path and also requires that the heads of the bolts fit into the precision machined slots of the shield. Furthermore, the described windage shield has an L-shaped cross-section with a portion which extends parallel to the direction of fluid flow within the fluid flow channel with the described intent of directing the main fluid flow past bolt heads on the opposite side of the bolted flange. However, this extended portion does not eliminate flow over the bolt heads due to secondary circulating fluid fields. Thus, it would be desirable to have a windage shield which does not extend into the fluid flow channel and which does not require the specialty designed bolt heads or a plurality of precision machined slots for receiving each of the bolt heads and which accommodates secondary fluid flows.